I was told that the Churchs law permits Catholics to satisfy their Sunday obligation at a schismatic orthodox ceremony, and that this was the case both before and after Vatican II. Is this true?
The authority that you quote (Catholic Family Radio) defends the opinion that it was and is permitted to satisfy this obligation of assisting at Mass in a schismatic church before and after Vatican II. It quoted Canon 1258 of the 1917 Code of Canon Law, and the shameful Canon 844 of the 1983 Code of Canon Law on the sharing of sacraments with non-Catholics. However, I am sorry to inform you neither of these Canons is relevant to the question at stake.